1. Field of the Invention
This invention relates to apparatus and process for film wrapping a packaged product. More specifically it is related to specifically designed apparatus and process which avoid the tendency of the wrapping film to cause unevenness in the pulling of the wrapping film which results in twisting of the film. Still more specifically the apparatus and process are equipped with a pair of film tracking, preferably electrostatic, probes spaced from the film and equipped to deposit static charges on the film. These static charges on the film inhibit any tendency of the film to cause the twisting which might otherwise result.
2. State of the Prior Art
Various commercial techniques and apparatus for wrapping packaged products with film are well known. In these of film is fed into an apparatus which folds the film around the package, provides for an overlapping of longitudinally extending edges of the film at the bottom of the apparatus and an appropriate sealing thereof.
Wherever there is a pulling of the film to wrap it around the packaged product, there is the likelihood of having an uneven pulling of the film, resulting in a twisting of the film particularly along the sides of the packaged product which results in a breakdown of the wrapping operation. This uneven pulling of the film may be caused by variations in the thickness of the film, variations in the thickness of coating material on the film, variations in the coefficient of friction on the surface of the film, etc.
In applicant's parent application Ser. No. 07/901,699 a number of U.S. Patents were cited. The patents on which rejection was based were Ramsey et al U.S. Pat. Nos. 4,433,527, Cerf 4,945,709, Ramsey 4,947,605, Shankl in 4,419,855, Kuippers 4,295,322 and Borrello 4,004,399. However the disclosures of electrostatic charges in these references are directed to the sealing of overlapping edges of the wrapping film.
There is no showing in the prior art of any apparatus or process which deposits a static charge on the wrapping film to avoid uneven pulling on the wrapping film.